This application relates to a container structure for a dangerous material such as gasoline, pesticide, toxic waste, etc. It relates particularly to a container structure which is especially designed to resist a direct impact thereon without becoming damaged and causing its contents to be released into the environment. Further, it relates to a container structure which minimizes heat transfer to the dangerous material in the event of an external fire.
Through the years, it has been conventional to store dangerous material such as gasoline, pesticide, toxic waste, etc. in tanks that are buried in the ground. However, a problem which has surfaced in connection with tanks that are buried in the ground is leakage of the dangerous material into the ground, and contamination of the environment and aquifer.
There have also been suggestions for providing above-ground storage facilities for dangerous materials such as gasoline. For example, U.S. Pat. No. 2,558,694 discloses an example of an above ground storage apparatus for gasoline. In that patent, an outer container having a volume of water surrounds an inner container that contains the gasoline. The water if freely flowable in the outer container. In the event of a fire, water is caused to flow through the outer container to dissipate heat.
Further, Dixon U.S. Pat. No. 4,469,129 discloses another type of above-ground container structure for dangerous material. The principal structure of the Dixon patent is an inner container for the dangerous material, an outer container surrounds the inner container, a normally static body of water disposed between the containers, and a layer of closed cell insulation secured to the inner container. The principal function of the structure disclosed in the Dixon patent is to minimize heat transfer to the dangerous material stored in the inner container, and to minimize leakage of dangerous material out of the inner container.
With above ground container structures for dangerous materials, an important problem that has to be addressed is crash protection. Often, such container structures are, of necessity, located in areas where heavy vehicles (e.g. trucks) operate. Thus, there is always a possibility of a heavy vehicle such as a truck directly impacting the container structure. If an impact causes the contents of the container structure to spill into the environment, the results can be very destructive. The Dixon patent specifically suggests the provision of a crash protection ring around the container structure to help minimize the likelihood of damage to the container structure due to an impact. Further, the Dixon patent discloses an embodiment in which the container structure may rest on the ground, and applicants believe that such a container structure may be able to slide somewhat if directly impacted by a vehicle. However, in the Dixon patent, the body of water between the inner and outer containers can be substantially displaced in the event of an impact. Thus, the containers can shift relative to each other in the event of an impact. An impact from a truck moving at a significant rate (e.g. 30 m.p.h.) may displace the containers sufficiently to damage the inner container, and cause its contents to spill into the environment.